I think @SoNic67 's contribution is useful to those of us reading in other parts of the world. When I first read the earlier comments about seeing message rates around 1200 a second with around 60-70 aircraft, my first thought was “what’s wrong with my setup?” - in the last seven days, the highest message rate I’ve seen was 600/sec with 100 aircraft.
After thinking about it I remembered this thread: https://discussions.flightaware.com/t/overload-on-the-use-of-surveillance-radar/76593
Clearly, the message rate is significantly influenced by the number and operating mode of the SSRs interrogating aircraft visible from any particular location, so it isn’t a particularly useful parameter for comparing setups unless they are looking at the same patch of sky.